The invention entails devices and methods for selectively vaporizing unwanted body tissues, such as excess tissue in the male prostate gland or a tumor, without damaging adjoining tissues.
Benign prostatic hyperplasia or xe2x80x9cBPHxe2x80x9d, commonly referred to as an enlarged prostate, affects more than 50% of men over age 55 and is a worldwide problem. Approximately 200,000 surgeries to treat this condition are presently performed each year in the United States at a cost estimated at $1.6 billion annually. While pharmaceuticals, such as terazosin, may limit prostate growth for a period of time, eventually a surgical solution may be required.
The long standing surgical procedure for treating BPH is transurethral resection of the prostate or TURP, in which an electrosurgical loop heated by radiofrequency (xe2x80x9cRFxe2x80x9d) energy is moved to and fro within the prostate to resect (cut out) troughs of prostate tissue. While a TURP produces satisfactory voiding of urine, it requires general anesthesia and an hour or more of costly operating room time and entails up to 15% impotence, 5-10% permanent incontinence and bleeding requiring a transfusion in up to 10% of the patients. In addition, most TURP patients suffer from retrograde ejaculation, and up to 30% or more of TURP patients experience an infection or other adverse effect.
Recently, high powered RF roller ball devices have been introduced, which have somewhat reduced the bleeding and other adverse effects of a TURP. However, the use of RF roller ball devices requires general anesthesia and an hour or more of costly operating room time. Holmium lasers can be used for resection of the prostate, producing urine flow results equal to a TURP, while eliminating bleeding and most of the other adverse effects of the above described procedures using RF energy. However, Holmium laser resection typically requires one hour or more of expensive operating room time and general anesthesia.
The interstitial (within tissue) use of microwave, laser or RF energy to thermally coagulate a portion of the prostate, while taking less time and avoiding general anesthesia, does not significantly reduce the prostate""s volume and thus produces less urine voiding relief than a TURP, high power RF roller ball or Holmium laser resection procedure. In addition, the patients treated with interstitial coagulating devices experience dysuria and discomfort for weeks after the procedure. If the tissue immediately underlying the urethra, which constitutes the exterior surface of the lobes of the prostate, is coagulated, the urethra dies, due to loss of its blood supply, leaving an open, irritating wound. The coagulated tissue then sloughs off and is excreted in the urine over a period of 3-6 weeks.
It would be desirable to be able to remove a sufficient amount of prostate tissue to provide immediate voiding and relief of BPH symptoms, while protecting the urethra and the immediately underlying tissue from damage, in a short, outpatient procedure, preferably in an outpatient treatment facility or a physician""s office under local anesthesia and/or sedation.
Laser or RF energy can be used to coagulate a tumor, but coagulation occurs irregularly, as conduction of heat through tissue of differing densities and water content is not uniform. Consequently, it is necessary to closely observe the coagulation procedure to avoid damaging nearby blood vessels, nerves and other vital tissues. While a vaporization zone can be distinguished from normal tissue by ultrasound imaging, coagulated tissue cannot be differentiated from normal tissue by ultrasound imaging. As a result, expensive magnetic resonance imaging (MRI) equipment would be required to visually monitor the coagulation procedure, so that the process can be halted if the coagulation zone approaches important blood vessels, ducts, nerves or other tissues. Unhappily, the use of MRI equipment would increase the cost of an already expensive procedure.
It would be desirable to be able to accurately vaporize a tumor of any shape, while directing laser energy away from a vital blood vessel, duct, nerve or other tissue adjoining the tumor, with the ability to observe the vaporization process using a less costly ultrasound imaging system.
The present invention provides for the vaporization of unwanted tissue in a mammalian body, without producing excessive coagulation of surrounding tissues and avoiding thermal damage to a nearby mucosal surface or an adjacent, important blood vessel, duct, nerve or other structure.
This is achieved by a catheter device adapted to deliver energy from a laser source to a body tissue, which device includes an elongate, sharp-ended hollow tube having first and second ports spaced from one another, a flexible energy conduit, adapted for connection to a laser source at its proximal end, a fluid conduit for passing a fluid through said ports for cooling and cleaning the distal end of the energy conduit, and a separate conduit for withdrawing fluid and hot gasses from the vaporization of tissue into the hollow tube.
The fluid can be passed through the ports by positive pressure, and gasses can be withdrawn by vacuum, i.e., negative pressure. The distal end of the flexible energy conduit is adapted to emit energy to a predetermined tissue site so as to ablate or vaporize the tissue.
In one embodiment of the device embodying the present invention, energy, such as laser energy, is transmitted through an optical fiber, whose distal radial end is beveled at an angle about 30xc2x0 to about 50xc2x0, preferably about 39xc2x0 to about 40xc2x0, into a prism-like shape, encased within a quartz or fused silica capillary tube and disposed within a metal tube with a sharp distal end, such as a syringe needle. Encasing the optical fiber in a capillary tube provides a significant difference in refractive index (air at 1.0 versus quartz or fused silica at about 1.33) at the beveled surface, which enables total internal reflection of emitted energy. As a result, energy is emitted from a port in the metal tube at an angle of approximately 80xc2x0 to about 90xc2x0 transverse to the axis of the optical fiber.
Two unique fluid channels and ports in the tube enable fluid to be infused through one channel in the metal tube to cool the distal end portion of the optical fiber as well as the internal face of the distal end of the metal tube, cool and clean the distal closed end face of the capillary tube from which the energy is emitted. Negative pressure applied through the other channel in the tube may also be used to evacuate the cooling fluid and the hot gasses from the vaporization of tissue, avoiding the excess coagulation of tissue surrounding the target area by thermal conduction.
An outer sheath of fluorinated hydrocarbon such as Teflon(copyright), a product of DuPont de Nemours of Wilmington, Del., other plastic material, or a ceramic may be employed around the sheath containing the optical fiber to facilitate penetration of tissue, prevent tissue adherence and provide insulation to avoid thermal damage to tissue from heat conducted along the needle.
In use, the present device is inserted into tissue and oriented to emit laser energy in a desired pattern, away from a region or tissue to be preserved, such as the mucosa or endothelial surface of an organ or an important blood vessel, duct, nerve or other structure, to prevent thermal damage thereto. The device can be rotated in an arc while lasing, or advanced and/or withdrawn while lasing, or both. Such a device, for example, could be used to vaporize a portion of the lobes of the prostate, without damaging the sensitive urethra, or its immediately underlying, supportive tissue, or to vaporize a tumor, without damaging surrounding normal tissue or a nearby major blood vessel, duct, nerve or other structure.